Background: Stage III gastric cancer patients had poor prognosis. This study aims to evaluate prognostic factor of stage III gastric cancer. Methods: We retrospectively studied 126 patients who were treated for stage III gastric cancer from Jan. 2007 to Dec. 2010 at Korea University Hospital and performed complete follow up for five years. Long-term survivor was defined more than five years survivor after gastrectomy. Results: Long-term survivor was 70 patients (55.6%). Tumor size, lymph node involvement, lymphatic invasion, venous invasion and neural invasion had prognostic significance on univariate analysis. But location of tumor, gross type, depth of invasion, TNM stage, combine resection, complication, histologic differentiation, type of operation and adjuvant treatment had no prognostic significance. The most common recurrence pattern was peritoneal recurrence (57.4%) according to analysis of recurrence pattern. The disease free survival according recurrence pattern was peritoneal recurrence (21.3 months), hematogenous recurrence (32.1 months), distant lymph node recurrence (12.0 months) and locoregional (12 months). The disease specific survival according recurrence pattern was peritoneal recurrence (9.2 months), hematogenous recurrence (11.3 months), distant lymph node recurrence (16.2 months) and locoregional (26.9 months). Conclusions: Lymph node involvement were the most significant prognostic factors on stage III gastric cancer after curative resection. Therefore, postoperative surveillance and adjuvant therapy were very carefully selected in stage III gastric cancer patient with extensive lymph node metastasis.